Key Points

Median progression-free survival was 23.8 months in the ribociclib arm compared with 13.0 months in the placebo arm.

The overall response rate was significantly higher among patients with measurable disease at baseline in the ribociclib arm compared with the placebo arm (51% vs 36%).

As expected, the most frequent adverse event was neutropenia, which was reported in 76% of patients in the ribociclib arm compared with 8% in the placebo arm. Grade 3/4 neutropenia was reported in 61% of patients in the ribociclib arm compared with 4% in the placebo arm, but it was asymptomatic in most patients.

“Three anticancer therapeutics that target cell-cycle mediators CDK4 and CDK6, so-called CDK4/6 inhibitors, have been approved by the U.S. Food and Drug Administration for use in combination with hormonal drugs—either aromatase inhibitors or fulvestrant—for treating postmenopausal women with HR-positive, HER2-negative advanced breast cancer,” said Debu Tripathy, MD, Professor of Medicine and Chair of the Department of Breast Medical Oncology at The University of Texas MD Anderson Cancer Center. “These new therapeutics have not yet been evaluated in a dedicated large, randomized trial as a potential treatment for the 30% to 40% of women with hormone receptor–positive, HER2-negative advanced breast cancer who are pre- or perimenopausal.”

“MONALEESA-7 is the first clinical trial to have the statistical power to show that ribociclib has clinical benefit specifically for pre- and perimenopausal women with hormone receptor–positive, HER2-negative advanced breast cancer,” continued Dr. Tripathy. “It is also the first trial to show that ribociclib can be safely and effectively combined with either tamoxifen or a nonsteroidal aromatase inhibitor together with ovarian suppression using goserelin.”

MONALEESA-7 Findings

Among the 672 patients enrolled in the clinical trial by Dr. Tripathy and colleagues, 335 were randomly assigned to ribociclib in combination with either tamoxifen or a nonsteroidal aromatase inhibitor (letrozole or anastrozole) and goserelin (Zoladex), and 337 were randomly assigned to placebo in combination with the same oral hormonal therapy options and goserelin. The primary endpoint of the trial was progression-free survival.

The study met its primary endpoint: Progression-free survival was significantly improved in the ribociclib arm compared with the placebo arm. Median progression-free survival was 23.8 months in the ribociclib arm compared with 13.0 months in the placebo arm.

Data are available for some of the secondary endpoints. For example, the overall response rate was significantly higher among patients with measurable disease at baseline in the ribociclib arm compared with the placebo arm (51% vs 36%).

As expected, the most frequent adverse event was neutropenia, which was reported in 76% of patients in the ribociclib arm compared with 8% in the placebo arm. Grade 3/4 neutropenia was reported in 61% of patients in the ribociclib arm compared with 4% in the placebo arm, but it was asymptomatic in most patients; neutropenia associated with fever and infection was reported in 2% of patients in the ribociclib arm and 1% in the placebo arm. Other adverse events included hot flashes, nausea, leukopenia, and joint pain/stiffness. Adverse events leading to permanent discontinuation of treatment occurred in 4% of patients in the ribociclib arm compared with 3% in the placebo arm.

“Longer follow-up is needed to determine whether the trial will meet its secondary endpoint of overall survival,” concluded Dr. Tripathy.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.